Nonhydrostatic ICosahedral Atmospheric Model (NICAM)

Institutions: RIKEN Advanced Institute of Computational Science (AICS), Japan &
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Japan &
University of Tokyo, Japan

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Description:

The Nonhydrostatic ICosahedral Atmosphere Model (NICAM) was developed for uses on the Earth Simulator. The prognostic variables are density, momentum, total energy, and tracer species. Sound waves are computed explicitly in horizontal and implicitly in vertical. The A-grid arrangement is adopted for the prognostic variables horizontally, that is, all of the prognostic variables are positioned at the centers of hexagonal cells. The Finite-Volume method is used for the spatial discretization of operators. The icosahedral grids are developed and optimized by the spring-dynamics method of Tomita et al. (2002). It supports a variable resolution mesh by stretching (Tomita 2008). The finite-volume method is used for the second-order accurate horizontal discretizations of divergence and gradient (Tomita et al. 2001). Tracers are transported by an upwind-bosed scheme using a linear reconstruction (Miura 2007). A three-stage Runge-Kutta scheme is supported, but the two-stage Runge-Kutta scheme is used usually.

Although NICAM was originally developed for the Earth Simulator, it works currently on a variety of computers including K-computer newly developed in AICS, Kobe, Japan.

An example of the NICAM simulation is below (Miura et al. 2007), which compares observed TBB (LEFT, MTSAT-1R) with simulated OLR (RIGHT, NICAM).

Typical horizontal resolutions, physics and dynamics time steps, and dissipation coefficients:

Information on the computational grid:

Icosahedral hexagonal grid, optimized via spring dynamics

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Test Case Results

Pure Advection

• 1-1: 3D deformational flow [with--ppm-vertical-remap | old--version]
• 1-2: 3D Hadley-like meridional circulation
• 1-3: 3D Horizontal advection of thin cloud-like tracers in the presence of orography

Rotating planet: From hydrostatic to non-hydrostatic scales

• 3-1: Non-orographic gravity waves on a small planet

Simple planet: From hydrostatic to non-hydrostatic scales

• 4-1-x: Dry baroclinic instability on a shrinking planet with dynamic tracers EPV and theta reduction factorls 1, 10, 100, 1000 to enable extreme grid spacings down to \delta x \approx 110m

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References:

• http://nicam.jp/
• Tomita,H., Tsugawa,M., Satoh,M., Goto, K.(2001) : Shallow water model on a modified icosagedral geodesic grid by using spring dynamics. J. Comp. Phys., 174, 579-613
• Tomita, H., Satoh, M., Goto, K.(2002) : An optimization of icosahedral grid by using spring dynamics. J. Comp. Phys., 183, 307-331
• Tomita, H. and Satoh, M. (2004) : A new dynamical framework of nonhydrostatic global model using the icosahedral grid. Fluid Dyn. Res., 34, 357-400.
• Miura,H., Satoh, M., Nasuno, T., Noda, A.T., Oouchi, K. (2007) : A Madden-Julian Oscillation event simulated using a global cloud-resolving model. Science, 318, 1763-1765.
• Miura, H., 2007: An Upwind-Biased Conservative Advection Scheme for Spherical Hexagonal–Pentagonal Grids. Mon. Wea. Rev., 135, 4038–4044.
• Satoh, M., T. Matsuno, H. Tomita, H. Miura, T. Nasuno, S. Iga, (2008) : Nonhydrostatic Icosahedral Atmospheric Model (NICAM) for global cloud resolving simulations. Journal of Computational Physics, the special issue on Predicting Weather, Climate and Extreme events, 227, 3486-3514, doi:10.1016/j.jcp.2007.02.006.
• Tomita, H. (2008) : A stretched grid on a sphere by new grid transformation. J. Meteor. Soc. Japan, 86A, 107-119.

Members of this modeling group during DCMIP-2012 and room location:

Room: FL1003